The present invention relates to a motor-driven compressor, and more particularly to a motor-driven compressor to be mounted on a vehicle.
Hybrid vehicle that is powered by both engine and electric motor varies the ratio of engine drive to motor drive in accordance with its running condition. In such hybrid vehicle, if a compressor that operates a refrigeration cycle of an air conditioner is driven by the engine of the vehicle, the compressor cannot obtain necessary drive force constantly from the engine. In a hybrid vehicle, therefore, a compressor that is driven by electric power from a battery mounted on the vehicle is used. Such motor-driven compressor is mounted on the body or engine of the vehicle.
The compressor is driven only by the electric motor when the engine is at a stop, such as during an idle stop. When the compressor is driven with the engine at a stop, noise is developed due to the operation of the compressor. Main cause of the noise development is the resonance due to the vibration of the body or engine caused by the vibration of the compressor transmitted via its mounting rather than the sound radiated from the compressor. Various mountings for a motor-driven compressor has been proposed to reduce the vibration transmission from the compressor to the body or engine of the vehicle.
Japanese Unexamined Utility Model Application Publication No. 64-44810 discloses a compressor having cylindrical fittings fixed thereto and used for mounting the compressor to an engine block. Tightening the bolts inserted through the cylindrical fittings into the threaded hole of the engine block, the compressor is mounted to the engine block. A rubber cushion is wrapped around the cylindrical fitting. The cylindrical fitting thus having the rubber cushion wrapped therearound is mounted to the compressor by using a bracket having a curled portion holding therein the cylindrical fitting and screwed to the outer surface of the compressor. The rubber cushion is provided between the bracket and the cylindrical fitting and between the compressor and the cylindrical fitting.
In the compressor disclosed in the publication No. 64-44810 wherein the cylindrical fitting provided on the compressor is held by the bracket screwed to the compressor, however, the cylindrical fitting is not mounted firmly to the compressor because of the rubber cushion provided between the bracket and the cylindrical fitting and the cylindrical fitting and the compressor. This causes displacement of the compressor during operation, so that the compressor vibrates with a large amplitude. The displacement of the compressor may damage the connection between the compressor and the refrigeration circuit. The large-amplitude vibration of the compressor may be transmitted to a vehicle and, therefore, passengers of the vehicle may be subjected to undesired vibration and noise.
The present invention is directed to providing a motor-driven compressor that allows reduction of noise in a vehicle and provides a rigid mounting for the compressor.